This is useful for normal replication in order to refresh the slave
when we are persisting on disk, but for diskless replication the
child is already receiving data while in WAIT_BGSAVE_END state.
If we turn from diskless to disk-based replication via CONFIG SET, we
need a way to start a BGSAVE if there are slaves alerady waiting for a
BGSAVE to start. Normally with disk-based replication we do it as soon
as the previous child exits, but when there is a configuration change
via CONFIG SET, we may have slaves in WAIT_BGSAVE_START state without
an RDB background process currently active.
Fdset target is used when we want to write an RDB file directly to
slave's sockets. In this setup as long as there is a single slave that
is still receiving our payload, we want to continue sennding instead of
aborting. However rio calls should abort of no FD is ok.
Also we want the errors reported so that we can signal the parent who is
ok and who is broken, so there is a new set integers with the state of
each fd. Zero is ok, non-zero is the errno of the failure, if avaialble,
or a generic EIO.
We need to remember what is the saving strategy of the current RDB child
process, since the configuration may be modified at runtime via CONFIG
SET and still we'll need to understand, when the child exists, what to
do and for what goal the process was initiated: to create an RDB file
on disk or to write stuff directly to slave's sockets.
With the exception of nodes sending MEET packets: we have to trust them
since they can send us MEET packets only when the cluster is initially
created or because sysadmin manual action.
In the cluster evaluation function we are supposed to set the cluster
state as "fail" if we are among a minority, however the code was not
detecting to be into a minority partition if exactly half the masters
were reachable, which is a minority.
However we don't try to do this if the integer is already inside a range
representable with a shared integer.
The performance gain appears to be around ~15% in micro benchmarks,
however in the long run this also helps to improve locality, so should
have more, hard to measure, benefits.
Some language in the comment was difficult
to understand, so this commit: clarifies wording, removes
unnecessary words, and relocates some dependent clauses
closer to what they actually describe.
I also tried to break up longer chains of thought
(if X, then Y, and Q, and also F, so obviously M)
into more manageable chunks for ease of understanding.
- Remove trailing newlines from redis.conf
- Fix comment misspelling
- Clarifies zipEncodeLength usage and a C API mention (#1243, #1242)
- Fix cluster typos (inspired by @papanikge #1507)
- Fix rewite -> rewrite in a few places (inspired by #682)
Closes#1243, #1242, #1507
The old DEBUG POPULATE form for automatic creation of test keys is:
DEBUG POPULATE <count>
Now an additional form is available:
DEBUG POPULATE <count> <prefix>
When prefix is not specified, it defaults to "key", so the keys are
named incrementally from key:0 to key:<count-1>. Otherwise the specified
prefix is used instead of "key".
The command is useful in order to populate different Redis instances
with key names guaranteed to don't collide. There are other debugging
uses, for example it is possible to add additional N keys using a count
of N and a random prefix at every call.
Following the CLIENT LIST output format, we prefix the unix socket
address with a "/" so that it is different than an IPv4/6 address.
This makes parsing simpler.
Related to #2010.
This fixes a potential bug that was never observed in practice since
what happens is that the asynchronous connect returns ok (to fail later,
calling the handler) every time, so a ping is queued, and sent_ping
happens to always be populated.
Howver technically connect(2) with a non blocking socket may return an
error synchronously, so before this fix the code was not correct.
